Whenever the Runner passes all of the ice protecting this server, you and the Runner secretly spend 0, 1, or 2. Reveal spent credits. If you and the Runner spent a different number of credits, end the run.

[This means that in order for Caprice's ability to trigger on a current run, the latest the Corp can rez Caprice is at run step 2.3 of the approach to the innermost ice, when the runner has decided to continue towards this ice. This is the same window that this ice can be rezzed.

Rezzing Caprice after the runner passes the innermost ice is too late to have her ability trigger this run, because the next non-ice rez window after passing the innermost ice is 4.3, which is after Caprice's ability would trigger.]

If there is no ice protecting the server, Caprice Nisei’s ability still
triggers if she was rezzed before the run was initiated. [Official FAQ]

This card was heavily bemoaned around its launch as being un-fun and game-breaking. While it certainly can be un-fun (especially in RP, when combined with a Nisei token) I think it's an interesting card.
Irrespective of its entertainment value, it is incredibly strong once installed, but its trash cost weakens your R&D to digs. Its natural home is probably RP, where it can make a nigh-on unassailable remote late in the game. It also has great utility against crim, making account siphon hard to fire, or as a general puzzle piece to increase how taxing a server is - for example, on R&D behind some taxing ice.
Against it, it can certainly be played around - especially if the corp hasn't yet become rich.
Overall, a strong card with a suitably high influence cost.